Discrete electro-optic effect induced by multiscale nanoresonators

Recent experiments have revealed an unusual electro-optic (EO) effect in relaxor KTa1-xNbxO3 (KTN) crystals. Our study reveals that the frequency dependence of EO effect is discrete, which can be attributed to multiscale polar nanoregions (PNRs). Traditionally, the EO effect of relaxor KTN is typically attributed to the relaxation of PNR subject to an electric field. As the frequency increases, incomplete reorientation weakens the EO effect. In contrast, we reconsider the frequency response of the EO effect from a new perspective that resonance between PNRs and electric field. When the electric field frequency matches the characteristic frequency of the PNR or intrinsic resonant frequency of KTN sample, a strong EO effect occurs. Otherwise, the PNRs contribute little to the EO effect, and the EO effect contributed from the polarizable lattice is extremely weak. By considering the PNRs as nanoresonators, a classical mechanical oscillator subject to a harmonic force can describe the frequency dependence of the EO effect, which indicates that the discrete behavior of EO effect originates from the resonance between multiscale PNRs and the electric field instead of PNR relaxation under an electric field.